A composition including an olefin-based, an olefin-acrylate-based, a polyamide-based, or a polyester-based polymer is used as a hot melt composition to protect (waterproofing, dampproofing, dustproofing, electrical insulation, and fixation) an electronic component.
A hot melt composition capable of maintaining electrical insulation is used to protect an electronic component. Various improvements to a hot melt composition have been made. Specifically, examples of the improvements include a method for reducing water absorption of a hot melt composition, and a method for enhancing adhesion between an adherend (plastic material such as polyolefin and metal such as aluminum and copper) constituting an electronic component and a hot melt composition so as to prevent the entry of water or moisture.
Among various hot melt compositions, a polyamide-based hot melt composition may be used for an electronic component, with high regard for adhesion to an adherent. As a type of polyamide-based hot melt composition, a dimer acid-based polyamide is used in an electronic component. A “dimer acid-based polyamide” as referred to herein is a polyamide produced from the reaction of an acid component including a dimer acid and a diamine component as described below.
A dimer acid-based polyamide exhibits good adhesion to a plastic having relatively high polarity (e.g. polyvinyl chloride and polyethylene terephthalate), and a metal such as aluminum and copper. A dimer acid-based polyamide has, however, insufficient adhesion force to a substrate having an olefin structure with low polarity such as polyethylene and polypropylene. Furthermore, a dimer acid-based polyamide exhibits relatively high water absorption, which causes a problem in maintaining the performance of an electronic component.
Meanwhile, it is known that other polymer materials are added to a dimer acid-based polyamide for use in an electronic component so as to improve the electric properties of the electronic component.
Patent Literature 1 discloses that a carboxyl group-containing olefin and a dimer acid-based polyamide are mixed to produce a mixture composition for use in a temperature sensor and a thermosensitive heating wire.
According to the same literature, the composition (temperature sensitive polymer body) has excellent water absorption properties and mechanical properties (adhesion properties).
Patent Literature 2 discloses a hot melt adhesive composition of a mixture of a polyolefin, a polyolefin which contains an acid anhydride or a carboxyl group, and a dimer acid-based polyamide. The literature has disclosed that the hot melt adhesive composition has improved adhesion to various adherends such as polyethylene, polyvinyl chloride and metal, and improved damp-proof properties.
The compositions described in Patent Literatures 1 and 2 have, however, problems for use as a hot melt composition including poor flow stability, large viscosity change, and inferior thermal stability in a molten state. While various performance of a hot melt composition for an electronic component is required to be stable for a long time under high temperature, the compositions according to both of the literatures do not sufficiently satisfy the recent user's severe requirements.
Therefore, a polymer composition having low water absorption, excellent electrical insulation, good adhesion to plastic and metal, and small viscosity change is much needed in order to maintain the performance of an electronic component.